Remove system cron activities on slaves

We don't need any of these - since they're all things that just
operate normal system maint. If we want code to run on a slave,
we'll run it.

Change-Id: I5ccc3c50f2cf0272a1b4710063612b1352b7e1d6

modules/openstack_project/files/nodepool/scripts/prepare_node.sh

@@ -115,5 +115,12 @@ elif [ "$OS_FAMILY" == "RedHat" ] ; then
     fi
 fi
 
+# Remove cron jobs
+# We create fresh servers for these hosts, and they are used once. They don't
+# need to do things like update the locatedb or the mandb or rotate logs
+# or really any of those things. We only want code running here that we want
+# here.
+sudo rm -f /etc/cron.{monthly,weekly,daily,hourly,d}/*
+
 sync
 sleep 5